I've raced Production and Blown Gas Coupe at WOS, ECTA, and LTA. Here is my unofficial take: As long as "stuff" is mounted in the OEM postion with a piece that is reasonably OEM like, then it's o.k. Were there are questions is when "stuff" is present that wasn't available for that model year OR "stuff" not mounted in the OEM position and especially when aero "stuff" isn't exactly like stock. However, there is one rule that I do believe that does need some clarification: 5.E.1 paragraph 2' " The vehicle will be unaltered in height,..."